The present invention relates generally to radios and more specifically to radios for executing multiple communication protocols.
Each communication protocol has a separate radio frequency (RF) to intermediate frequency (IF) front end or processing channel, as well as specific sampling rates. This results in additional expense in hardware, PC board space, consumed power and hardware complexity. A typical example is illustrated in FIG. 1, wherein a GPS channel has its front end hardware connected to a digital signal processor (DSP), while a wireless local area network (WLAN) and a Blue Tooth network channel are connected through a multiplexer and shared A/D and D/A converters to the DSP. A frequency synthesizer must provide the appropriate, separate frequencies for the WLAN and Blue Tooth channels and separate frequencies to the A/D and D/A converters depending upon which signal is being transmitted through the multiplexer. The DSP controls the frequency synthesizer, the multiplexer and the A/D and D/A converters depending upon which channel is being processing.
The radio of the present invention includes a first channel for receiving signals at a first frequency and a second channel for receiving and transmitting signals at a second frequency. A multiplexer connects the first and second channels through an A/D and D/A converter to a digital signal processor. An oscillator is connected to and provides a common sampling frequency to the A/D and D/A converters. The digital signal processor controls the multiplexer and modifies the received digital signals to accommodate for the different carrier frequencies of the channels using the common sampling rate. A frequency synthesizer is connected to the oscillator and provides different frequency signals for the channels. A third channel may be provided for receiving and transmitting signals at a third frequency and is also connected to the multiplexer. The processor is capable of performing communication protocols for at least two of the channels simultaneously. While the first channel may be designed to receive GPS signals, the second channel may be designed for receiving one or more of WLAN, Blue Tooth, GSM, GPRS and WCDMA.
The radio may be a software-defined radio. The processor accommodates for the different frequency signals by linear interpolation of the sampling frequency. The linear interpolation for each interpolated sample Yn, at the desired sampling rate T0, is calculated from two samples Xn+1, Xn at the common sampling rate Ts as:Yn=Xn+n(T0−Ts)/Ts(Xn+1−Xn).
These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.